[Muscle physiology and the effect of muscle-tendon surgery in cerebral palsy].

The muscle reacts physiologically in neuromuscular disorders which do not affect muscle tissue directly (such as muscular dystrophies), and adapts to altered demands. For this reason, alterations in the muscle-tendon apparatus are grossly secondary. Changing load stimulates an increase in muscle fibres, whereas continuous pull results in an increase in collagen fibres (fibrosis). The length range in which a muscle produces force must be considered with respect to the range of motion of the joint in order to plan soft tissue corrections and to understand the postoperative result. An optimal correction of muscle length can increase muscle force whereas overlengthening will reduce it. The latter is desired in cases where spastic muscle force needs to be reduced. In contrast shortening the muscle-tendon apparatus may be indicated in order to correct overlength and to increase muscle force. The effect of intramuscular lengthening procedures, performed as an aponeurotomy or an intramuscular tenotomy, depends on the stretching program after surgery. Extramuscular tendon lengthening, on the other hand, results in an immediate length gain. The danger of overlengthening and consecutive muscle weakening, however, is greater with the tendinous procedures.